Linkage disequilibrium and spatial aggregation of genotypes in sexually reproducing populations of Erysiphe necator

Random mating and recombination in heterothallic ascomycetes should result in high genotypic diversity, 1:1 mating-type ratios, and random associations of alleles, or linkage equilibrium, at different loci. To test for random mating in populations of the grape powdery mildew fungus Erysiphe necator, we sampled isolates from vineyards of Vitis vinifera in Burdett, NY (NY09) and Winchester, VA (VA09) at the end of the epidemic in fall 2009. We also sampled isolates from the same Winchester, VA vineyard in spring 2010 at the onset of the next epidemic. Isolates were genotyped for mating type and 11 microsatellite markers. In the spring sample, which originated from ascospore infections, nearly every isolate had a unique genotype. In contrast, fall populations were less diverse. In all, 9 of 45 total genotypes in VA09 were represented by two or more isolates; 3 of 40 total genotypes in NY09 were represented by two or more isolates, with 1 genotype represented by 20 isolates. After clone correction, mating-type ratios in the three populations did not deviate from 1:1. However, even with clone correction, we detected significant linkage disequilibrium (LD) in all populations. Mantel tests detected positive correlations between genetic and physical distances within vineyards. Spatial autocorrelation showed aggregations up to 42 and 3 m in VA09 and NY09, respectively. Spatial autocorrelation most likely results from short dispersal distances. Overall, these results suggest that spatial genetic aggregation and clonal genotypes that arise during the asexual phase of the epidemic contribute to persistent LD even though populations undergo sexual reproduction annually.     

Improved method for determination and identification of serotonin in foods

A previously described method to identify and quantitate serotonin in foods has been improved. The extraction and separation of serotonin from interfering substances has been improved, and the scope of material to which the method may be applied has been widened. The relative standard deviation (RSD) for repeated determinations of serotonin in canned fried tomato purée and the average recovery of serotonin added to the same sample was 6.25 and 89.9%, respectively. The method showed the presence of serotonin in apricots, cherries, and peaches.     

Early T-maze behaviour and subsequent growth in commercial broiler flocks

Two batches of 2000 mixed-sex broiler chicks were obtained, one in summer and one in winter. Each flock was housed on the floor at a commercial farm. At 2 or 3 d of age, the latencies to escape from a T-maze were measured in 1044 and 1180 chicks in the summer and winter flocks, respectively. Chicks were assigned to high (HP), moderate (MP) or low (LP) performance categories if their escape latencies were below 40 s, between 40 to 90 s, or above 90 s, respectively. Ninety male and 90 female chicks from each of the 3 categories were weighed when they were 3 d old. The birds then remained undisturbed, apart from routine maintenance, until similar numbers were weighed at 49 d of age. Some birds may have been weighed at both ages. Body weights were higher in males than females and higher in the winter than summer flock at 3 d of age. Significant main effects of chick category as well as gender and season were found at 49 d of age. There were no significant interactions. As expected, 49-d body weights were higher in males than females and in the flock reared in winter than in summer. 5. HP chicks (those that showed rapid escape from the T-maze at 3 d) were also significantly heavier at 49 d than their LP counterparts, with MP chicks occupying an intermediate position. This suggests that early performance in a T-maze test is positively associated with subsequent growth. Furthermore, this relationship was apparent in each of the 2 flocks. Given this positive association, we suggest that this simple, rapid and non-invasive behavioural test could be a useful selection criterion for future breeding programmes.     

Hybrid chipboard panels based on sugarcane bagasse, urea formaldehyde and melamine formaldehyde resin

The expansion of Brazilian agricultural production was very important in the last decade. A number of waste residues were produced showing an enormous potential for industrial crops and products. Sugarcane bagasse is the most important one and it has been investigated for chipboard panel's preparation. In this sense, this work aims to develop, characterize and compare chipboard panels made with sugarcane bagasse with urea formaldehyde (UF) and melamine formaldehyde (MF) resins. Panels were obtained with a mixture of sugarcane bagasse and particles, like pine or eucalyptus, with and without paraffin in the formulation. Nine different types of panels have been made, all with 9% in resin mix, under a pressing cycle of 4.0 MPa cm², and temperature of 160 °C. Under physical tests, the panels complied with the American Standard CS 236-66 for trading chipboards of medium density and, in most cases the results obtained were lower than the ones raised in the literature. Under mechanical tests, that same standard was not complied with and, in most cases the results were close to or higher than those obtained in the literature.     

Euparyphium albuferensis and Echinostoma friedi (Trematoda: Echinostomatidae): experimental cercarial transmission success in sympatric snail communities

Euparyphium albuferensis and Echinostoma friedi cercarial infectivity to four species of sympatric snails was examined under single- or multiple-choice laboratory conditions to show the level of parasite-snail host compatibility. Radix peregra, Lymnaeafuscus, Physella acuta and Gyraulus chinensis act as second intermediate hosts of both parasite species although different cercarial transmission success (CTS) was observed. In single-host experiments, R. peregra and P. acuta showed a high degree of compatibility with E. albuferensis, while only P. acuta in the case of E. friedi. In two-choice snail communities, a snail with high CTS increased the values of another with low compatibility, in both parasite species. In multiple-choice snail communities, high CTS of some hosts decreased, while low CTS of other hosts increased. The degree of parasite-host compatibility of each snail species could be determined by the presence of other snails in the community.     

Spatiotemporal characterization of citrus postbloom fruit drop in Brazil and its relationship to pathogen dispersal

Citrus postbloom fruit drop (PFD) is caused by Colletotrichum acutatum and C. gloeosporioides. These pathogens attack the flowers and cause premature fruit drop and the retention of fruit calyces. This study was designed to characterize the spatial and temporal dynamics of PFD in commercial citrus‐growing areas to better understand the disease spread. Experiments were carried out in three young orchards (500 trees each) in two municipalities in Sao Paulo State, Brazil. Symptoms of PFD on the flowers and presence of persistent calyces were assessed in each of three orchards for three years. Logistic, Gompertz and monomolecular models were fitted to the incidence data over time from the trees with symptoms. The spatial pattern of diseased trees was characterized by a dispersion index and by Taylor′s power law. An autologistic model was used for the spatiotemporal analysis. The logistic model provided the best fit to the disease incidence data, which had a fast progress rate of 0·53 per day. During the early epidemic of PFD, the spatial pattern of diseased trees was random, which suggested that inoculum spread was due to mechanisms other than rain splash. As the disease incidence increased (up to 12·6%), the spatial pattern of diseased trees became aggregated. The rapid rate of disease progress and the distribution of PFD suggest that dispersal of the pathogen is possibly related to a mechanism other than splash dispersal, which is more typical of other fruit diseases caused by Colletotrichum spp.     

Nature and lability of northern Adriatic macroaggregates

The key organic constituents of marine macroaggregates (macrogels) of prevalently phytoplankton origin, periodically occurring in the northern Adriatic Sea, are proteins, lipids and especially polysaccharides. In this article, the reactivity of various macroaggregate fractions in relation to their composition in order to decode the potentially »bioavailable« fractions is summarized and discussed. The enzymatic hydrolysis of the macroaggregate matrix, using α-amylase, β-glucosidase, protease, proteinase and lipase, revealed the simultaneous degradation of polysaccharides and proteins, while lipids seem largely preserved. In the fresh surface macroaggregate samples, a pronounced degradation of the α-glycosidic bond compared to β-linkages. Degradation of the colloidal fraction proceeded faster in the higher molecular weight (MW) fractions. N-containing polysaccharides can be important constituents of the higher MW fraction while the lower MW constituents can mostly be composed of poly- and oligosaccharides. Since the polysaccharide component in the higher MW fraction is more degradable compared to N-containing polysaccharides, the higher MW fraction represents a possible path of organic nitrogen preservation. Enzymatic hydrolysis, using α-amylase and β-glucosidase, revealed the presence of α- and β-glycosidic linkages in all fractions with similar decomposition kinetics. Our results indicate that different fractions of macroaggregates are subjected to compositional selective reactivity with important implications for macroaggregate persistence in the seawater column and deposition.     

伏马镰刀毒素B1(FB1)影响猪只细胞因子并降低免疫抗体效价之探讨

伏马镰刀毒素B1（FB1）主要由遭污染的玉米轮状镰刀霉菌（F.verticillioides）所产生,具有细胞毒性与致癌性。本试验将建立一个仔猪的活体模式以分析FB1对于细胞因子作用平衡网络的影响,并探讨长期低浓度的毒素暴露对疫苗抗体反应的最终影响。